Engineered Promoter-Switched Viruses Reveal the Role of Poxvirus Maturation Protein A26 as a Negative Regulator of Viral Spread.
Engineered Promoter-Switched Viruses Reveal the Role of Poxvirus Maturation Protein A26 as a Negative Regulator of Viral Spread.
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DOI：
10.1128/jvi.01012-21
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发表时间：
2021-09-09
影响因子：
5.4
通讯作者：
Maluquer de Motes C
中科院分区：
文献类型：
--
作者：
Holley J;Sumner RP;Lant S;Ribeca P;Ulaeto D;Maluquer de Motes C
牛痘病毒产生两种类型的病毒粒子，称为单膜细胞内成熟病毒（MV）和双膜细胞外包膜病毒（EV）。当初始MV进一步包裹并分泌以在宿主内传播感染时，EV产生更早达到峰值。然而，在感染后期，MV在细胞内积累，并成为宿主到宿主传播的重要因素。调节这种开关的过程仍然难以捉摸，被认为是受宿主因素的影响。在这里，我们研究了EV和MV的生产是由病毒通过表达F13和MV特异性蛋白A26调节的假设。通过切换启动子和改变F13和A26的表达动力学，我们证明A26表达下调EV产生和噬斑大小，从而限制病毒传播。该过程与A26与MV表面蛋白A27的结合和F13的排除相关，从而降低EV滴度。因此，MV成熟由病毒A26蛋白的丰度控制，与其他因素无关，并且是EV产生的速率限制。A26基因在脊椎动物痘病毒中是保守的，但在已知仅通过咬人的节肢动物传播的痘病毒中却明显丢失。因此，A26介导的病毒成熟似乎是一种古老的进化适应，以增强痘病毒的传播，痘病毒随后从适应载体的物种中丢失，A26可作为遗传标记。病毒调节机制的存在，以产生适应履行不同功能的病毒粒子代表了一个新的复杂性水平的哺乳动物病毒的进化，适应和传播的重大影响。重要性脊索痘病毒是哺乳动物病毒，其独特地产生适于在宿主内传播的第一类型病毒粒子和增强宿主之间传播的第二类型病毒粒子，其可以通过多种方式发生，包括直接接触、呼吸道飞沫、口腔/粪便途径或通过载体。两种病毒体类型对于平衡宿主内传播和宿主间传播都很重要，因此必须严格控制病毒成熟途径。在这里，我们提供的证据表明，病毒蛋白A26的表达丰度和动力学调节这一过程，防止形成的第一种形式和转向成熟的第二种形式。A26在产生子代病毒体的第一波之后较晚表达，因此确保了充分的病毒传播，并且A26提供了具有增强的环境稳定性的病毒体。A26在所有脊椎动物痘病毒中的保守性，但不是在那些只通过叮咬节肢动物传播的痘病毒中，揭示了A26控制的病毒成熟对于涉及环境暴露的传播途径的重要性。
Vaccinia virus produces two types of virions known as single-membraned intracellular mature virus (MV) and double-membraned extracellular enveloped virus (EV). EV production peaks earlier when initial MVs are further wrapped and secreted to spread infection within the host. However, late during infection, MVs accumulate intracellularly and become important for host-to-host transmission. The process that regulates this switch remains elusive and is thought to be influenced by host factors. Here, we examined the hypothesis that EV and MV production are regulated by the virus through expression of F13 and the MV-specific protein A26. By switching the promoters and altering the expression kinetics of F13 and A26, we demonstrate that A26 expression downregulates EV production and plaque size, thus limiting viral spread. This process correlates with A26 association with the MV surface protein A27 and exclusion of F13, thus reducing EV titers. Thus, MV maturation is controlled by the abundance of the viral A26 protein, independently of other factors, and is rate limiting for EV production. The A26 gene is conserved within vertebrate poxviruses but is strikingly lost in poxviruses known to be transmitted exclusively by biting arthropods. A26-mediated virus maturation thus has the appearance to be an ancient evolutionary adaptation to enhance transmission of poxviruses that has subsequently been lost from vector-adapted species, for which it may serve as a genetic signature. The existence of virus-regulated mechanisms to produce virions adapted to fulfill different functions represents a novel level of complexity in mammalian viruses with major impacts on evolution, adaptation, and transmission. IMPORTANCE Chordopoxviruses are mammalian viruses that uniquely produce a first type of virion adapted to spread within the host and a second type that enhances transmission between hosts, which can take place by multiple ways, including direct contact, respiratory droplets, oral/fecal routes, or via vectors. Both virion types are important to balance intrahost dissemination and interhost transmission, so virus maturation pathways must be tightly controlled. Here, we provide evidence that the abundance and kinetics of expression of the viral protein A26 regulates this process by preventing formation of the first form and shifting maturation toward the second form. A26 is expressed late after the initial wave of progeny virions is produced, so sufficient viral dissemination is ensured, and A26 provides virions with enhanced environmental stability. Conservation of A26 in all vertebrate poxviruses, but not in those transmitted exclusively via biting arthropods, reveals the importance of A26-controlled virus maturation for transmission routes involving environmental exposure.